Loss of androgen receptor expression is associated with aggressive tumor features and reduced survival in breast cancer patients

Androgen receptor (AR) is reported to be expressed in the majority of breast cancers (BC) with different expression rates across breast cancer subtypes. AR might influence cell proliferation, DNA damage repair, apoptosis, cellular migration and metastasis. The prognostic role of AR varies significantly across breast cancer subtypes. Here, we studied the expression pattern and prognostic relevance of AR in BC, with special focus on molecular stratification. We analyzed a large population-based cohort of breast carcinomas with long and complete follow up. AR expression was evaluated by immuno-histochemistry on tissue microarray slides. Loss of AR was significantly associated with features indicative of poor prognosis (larger tumor diameter, higher histologic grade, estrogen (ER) and progesterone hormone (PR) receptor negativity, elevated proliferation by Ki67, and expression of basal markers). Also, expression of AR was associated with lower proliferation by Ki67 regardless of ER-status. Regarding survival, loss of AR was significantly correlated with decreased breast cancer-specific survival in univariate analysis, both in the overall cohort and within the Luminal A and basal-like (CK5/6+) subgroups. In summary, AR expression emerged as a favorable prognostic factor in breast cancer, demonstrating independent prognostic significance within the basal-like (CK5/6+) subgroup.